Apparatus for controlling the release of bombs from aircraft



E. s. PETERSON 2,396,197

Filed Dec. :0, 1942 5 Sheets-Sheet 1 w .I ll $5M I J 25:8 28 T APPARATUSFOR CONTROLLING THE RELEASE OF BOMBS FROM AIRCRAFT inch 5, 19

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INVENTOR. EDWARD S. PETERSON ATTORNEYS NEH: mzuh amg'l 33946- E. s.PETERSON 2,395,219?

APPARATUS FOR CONTROLLING THE RELEASE OF BOMBS mom AIRCRAFT Filed Dec.30, 1942 5 Sheets-Sheet 3 INVENTOR- EDWARD S. PETERSON ATTORNEYS March53, 39.46 E. s. PETERSON APPARATUS FOR CONTROLLING THE RELEASE OF BOMBSFROM AIRCRAFT Filed. Dec. 30, 1942 5 Sheets-$heet 4 INVEN TOR. EDWARD S.PETERSON ATTORNEYS arch 1 E. s. PETERSON APPARATUS FOR CONTROLLING THERELEASE OF BOMBS FROM AIRCRAFT Filed Dec. 30, 1942 5 Sheets-Sheet 5 m N8 5 E m m Q m r' %milllllllllfllllllllllrll to g m L\\\\\\-\\\T\\K\\ m\\\\\\\\\\\\\\\\\\\w E. I l Tm\\-. ull-lum-rllnlilmmlll'ljjfli' I l nwlllllllllllll 1'1 1' id (.1 {g B u v I 'L 8 g 5 u I r0 a I m Y'd 7w O50a S u;

INVENTOR. EDWARD S. PETERSON ATTORNEYS Patented Mar. 5, 1946 APPARATUSFOR CONTROLLING THE RE- LEASE OF BOMBS FROM AIRCRAFT Edward S. Peterson,Elmwood Park, Ill., assignor to Automatic Electric Laboratories, Inc., acorporation of Delaware Application December 30, 1942, Serial No.470,590

10 Claims.

The present invention relates to apparatus for controlling the releaseof bombs from an aircraft and, more particularly, to improvements inapparatus for so timing the release of bombs from an aircraft that apredetermined spacing between bomb hits on an objective may be obtained.This application is a continuation-in-part of copending applicationSerial No. 451,513, filed July 18, 1942.

In certain bombing operations the maximum effectiveness is obtained byreleasing the bombs in trains and at spaced intervals, such that apredetermined spacing interval between hits on the objective isobtained. For example, in bombing troop columns, supply trains or thelike, the maximum destructive power'is obtained by releasing the bombsat such intervals that the zone of destruction of one exploding bomb ofthe train just overlaps the zone of destruction of the preceding andsucceeding bombs .of the train. The spacing between hits on such anobjective is, of course, determined by the ground speed of the aircraftfrom which the bombs are released and the time interval separationbetween the release of successive bombs of the train. To correlate thesefactors so that any desired spacing interval between bomb hits on theobjective may be obtained while the aircraft is traveling at apredetermined but variable speed, it is necessary to provide a devicefor measuring the time interval between the release of successive bombsof the train. Such a device must be readily adjustable to vary themeasured time intervals so that any desired spacing between bomb hits onthe objective may be obtained at any ground speed of the craft fromwhich the bombs are released.

It is an object of the present invention to provide electrical timingapparatus of the character described, which is of simple and ruggedconstruction, is easy to adjust and operate, is thoroughly reliable inoperation at any air pressure and under widely varying temperatureconditions, and is light in weight.

According to another object of the invention. provisions are made in theapparatus for preventing variations in the timing operations of theapparatus regardless of wide variations in the voltage of the currentsupply source from which the component parts of the apparatus areenergized.

In accordance with a further object of the invention, improvedfacilities are provided in the apparatus for insuring the start of thebomb release operations within a short predetermined time interval afterthe bomb release key, button or other device is operated.

According to still another object of the invention, provisions are madein the apparatus for adjusting the circuit equipment to obtain a desireduniform ratio between the bomb release intervals and the bomb spacingintervals, regardless of the periodicity of bomb release and regardlessof manufacturing variations in the component parts of the circuitequipment.

It is a further objct of the invention to provide improved, apparatus ofthe character described, which includes a 'presettable device forterminating the bomb release operations after a predetermined number ofbombs, determined by the setting of the device, have been released.

It is still another object of the invention to provide, in combinationwith bomb spacing interval control element of the apparatus, improvedindicating facilities which are so arranged that for any setting of thecontrol element the relationship between the ground speed of theaircraft and the spacing between bomb hits on the objective is clearlyindicated thereby.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the specification taken in connection withthe accompanying drawings in which Fig. 1 illustrates the circuitarrangement of improved bomb release timing apparatus, characterized bythe features of the present invention; Fig. 2 illustrates a modificationof the circuit arrangement shown in Fig. 1; and Figs. 3, 4, 5 and 6illustrate the mechanical construction and arrangement of improvedapparatus which may be wired either in accordance with the circuit shownin Fig. 1 or the circuit shown in Fig. 2.

Referring now more particularly to Fig. 1 of the drawings, there isschematically illustrated a bomb release mechanism I of theelectromagnetically controlled type now in use on modern bombing planes.Without regard to the mechanical construction of this mechanism, it maybe pointed out that the mechanism is adapted successively to release atrain of bombs from the bomb bay of the plane in which it is mounted, inresponse to a train of current impulses of corresponding numericalvalue. More specifically, the arrangement of the mechanism is such thatone bomb is released thereby in response to each received currentimpulse and the periodicity of the received impulses may be varied tocorrespondingly change the rate at which the bombs are released thereby.The arrangement of the mechanism may be such that the spacing intervalbetween the release of any two bombs of the train is determined eitherby the open-circuit or the closed-circuit period of the impulse. Ingeneral, however, the mechanism is so designed that for reliableoperation the received impulses should be divided equally as between themake and break periods thereof, this being true regardless of theperiodicity of the received impulses in a train.

In general, the improved apparatus for con trolling the transmission ofimpulses to the release mechanism I85 comprises a control tube I havinga timing network, which comprises the condenser I34 and the resistanceof the adjustable rheostat I02, included in the input circuit thereof,and a pulsing relay I50 having a winding adapted to be included in theoutput circuit of the tube I06 in series with the source of anodepotential I65 and an adjustable biasing resistor II". The electrondischarge tube I00 is of the well known pentode type having an anodeIIIIIa, a cathode I000, a cathode heater I00h, a control grid I00g and ascreen electrode "30s. Preferably this tube is of the well knowncommercial 25L6 type. The characteristics of this tube are such that ifa constant potential is maintained upon the screen electrode thereof andthe bias voltage impressed between the input electrodes I000 and I009.is maintained at a fixed value, the space current flow therethrough isheld substantially. constant regardless of Wide variations in thevoltage applied to the anode I00a thereof. Stated in other terms, thecharacteristics of the tube are. such that by holding the potential ofthe screen electrode I00s constant, wide variations in For the purposeof the output terminals of the source I65, a voltage regulatingarrangement is provided which comprises a gas filled electric dischargetube I38 shunting the output terminals of the source I65 in series. withthe voltage regulating resistor I39; The tube I38, whichmay be of thewell known neon type, for example, hasthe characteristic of maintaining.a substantially constant voltage acrossits electrodes regardless of themagnitude of, space current flow therethrough after the gas surroundingthese electrodes is ionized to provide which impulses. are produced bytheapparatus which would otherwise be caused by large changes in. thetemperature of the other circuit elements. Although any carbon orceramic resistor having the proper negative temperaturecoefiicient ofresistance may beused, the resistor I02 is preferably cf. the typemanufactured by the Keystone Carbon Company, Inc., of Saint Marys,Pennsylvania, havinga negative temperature coeflicient atx20 centigradeof..0.G2 ohm'/ohm/ centigrade.

The arrangement of the illustrated apparatus is such that the bombrelease mechanism I may be manually controlled by the bomb releaseswitch I61 to release the bombs held in the bomb bay of the craft one ata time, or automatically controlled to release a number of bombs in apredetermined train. To this end, a control switch I60 is provided, Thisswitch is of the snap-acting type and is provided with three positions,i. e'., a normal position wherein all of the contacts thereof aredisengaged, a train position wherein the contacts IGI and I62are-respectively engaged to condition the apparatus to release a trainof bombs in response to one operation of the switch I61,.and a selectposition wherein the In order visually to indicate to a bombardier thatthe switch I60 has been operated to its train position,.a signal lampI31 is provided.

For the puropse of counting the released bombs of a train and, morespecifically, that-of counting the impulses transmitted by thev pulsingrelay- I50 to the bomb release mechanism. Ii85, a presettable'countingdevice I10 is provided.- This device may be preset .to cause thereleaseof any desired numberof bombs in atrain and, operatinginconjunction with, the locking. relay I40, is arranged to terminate thetransmission of impulsesto the bomb release mechanism I85 afterbombs,'corresponding in number to the setting of the-device, have beenreleased by this mechanism; In order to initiate the operation of"theapparatus to cause the release of a train; of bombs at the exactinstant that the bombsight is. brought .to bear up-- on the leading endof an objective, the button or: key-operated; selferestoring switch I61is provided. Current forenergizing the control ele ments of the bombrelease mechanism. I85, the windings of the relays I40 and I50, thestepping. magnet I15 of thexcounting device: I10, the oathode heaterI00h, and thefilament of the signal lamp .I31 is derived from a currentsource I68.- For convenience in describing the circuits,. this source isshown as. abattery. In practice, however, this source may comprise a.smaltmoto'r' driven generator having-anoutput voltage that may vary overrather wide limits. This source may, in the usual installation, have. avoltage rating of approximately 26 volts. with an expected variation inthis voltage of. from 24 to 28.5 volts. If desired, a power switch: I68a maybe provided for disconnecting the positive or. ungroundedterminal of this source from the,illus-- trated circuit apparatus. Theindicated screen and anode voltage source I65 is, ineifect' a voltagestep-up device having its input terminals I651; arranged to be connectedacross the terminals of the current source I68; This device ispreferably of the mechanical vibrator typehaving an input voltage ratingequalto that of the source I68and. an output voltageratingofapproximately 200 volts. For the purpose of smoothing the directoutputv voltage appearingbeing secured together by means of assemt'ilyscrews 534. The various arts of the apparatus arehoused within a case400 upon which the front panel 300 is mounted by means of suitablemounting screws. More specifically considered, the above-identifiedparts of the apparatus are directly supported upon the sub-panel 30LThis sub-panel also carries sockets for receiving the control tube I00,the electric discharge tube I38 and the signal lamp I31 together with anoutlet socket 302 through which connections may be brought out to thecurrent supply source I68 and the contact springs of the bomb releaseswitch I61.

Briefly to consider the mechanical construction and arrangement of thecounting device I10, the details of which are best shown in Fig. 3 ofthe drawings, it will be noted that this device comprises a frame I10aupon which the spring pile-up I13 is mounted. One of the movable contactsprings of this pile-up is provided with a cam finger I13a which isnormally engaged by a control pin I12 to maintain the movable andstationary contacts carried by the springs of the pile-up out ofengagement. The pin I12 is carried by a detent wheel I1I which isrotatable with the ratchet wheel I 14 and a stub shaft I14a rotatablymounted on the frame I 10a. Rotation may be imparted to the shaft "Gaand the two wheels I14 and HI under the control of the pulsing relay I50by means of the stepping magnet I15 acting in conjunction with theillustrated pawl mechanism. More specifically, the magnet I15 is carriedby the frame Him and is provided with an armature I1 which carries atthe upper end thereof a pawl member I 11. This pawl member is mounted ona pivot in I18 extending between the inturned ends of the armature I16,and is provided with a stop part I11'a which is spring biased to engagethe left edge of the frame projection I19. The pawl finger of the memberI11 is normally restrained out of the path of rotation of the teeth onthe ratchet wheel I14 by means of a leaf spring I80 which is securedflatwise against the outer surface of the armature I16 and is providedwith an extended portion that engages the edge of the frame projection I19 opposite that engaged by the pawl member part I11a, From the aboveexplanation it will be understood that each time the magnet I15 isenergized to attract its armature I16, this armature is pivoted in acounterclockwise direction, as viewed in Fig. 3 of the drawings, againstthe bias of the leaf spring I80. Incident to this operation the pawlmember I11 is pivoted and translated until the pawl finger thereofengages one of the teeth of the ratchet wheel I14. Continued movement ofthe armature I16 toward the pole face of the magnet I15 serves to rotatethe shaft H411 and connected wheels I14 and HI in the clockwisedirection. The detent wheel I1I is provided for the purpose of insuringa precise and predetermined movement of the pin I12 in response to eachoperation of the magnet I15 and the associated pawl mechanism. To thisend a centering spring I1Ia is provided which is anchored at one end tothe frame Ia. The free end of this spring is provided with a return bentportion shaped accurately to conform to the tooth configuration of theteeth on the detent wheel I1I. By virtue of the arrangement of thedetent wheel Ill and the coacting centering spring I1Ia, this wheel andthe pin I12 carried thereby are moved through the same predeterminedangle in response to each energization of the stepping magnet I15,regardless of the length of the stroke imparted to the armature I15.

In performing a given counting operation, the device I10 functions tocount the number of steps required to return the pin I12 from apreselected off-normal position to its normal position wherein itengages the cam follower portion I13a of one of the movable springs inthe spring pile-up I13. In order to rotate the wheels I14 and HI for thepurpose of presetting the pin I12 to a desired offnormal position, theshaft I14a is provided with a portion which extends through openingsprovided in the two panels Bill and 300 and has mounted thereon a knobISI. This knob carries an indexing element I8Ia which, in cooperationwith a circular scale 403 inscribed or otherwise formed on the outersurface of the panel 30I, forms a convenient arrangement for indicatingthesetting of the "pin I12. More specifically, the indicia of the scale403 are suitably arranged to indicate the number of bombs which will bereleased during a given counting operation before the bomb releaseoperations are terminated. In this regard it will be understood thatsince the finger of the pawl member I11 is normally held out ofengagement with the teeth of the ratchet wheel I14, this wheel and thedetent wheel I1I may be rotated in either direction by suitablemanipulation of the knob I8I.

The mechanical construction and arrangement of the rheostat I92 and theindicating means associated therewith is best illustrated in Figs. 1, 5and 6 of the drawings. This rheostat is provided with a supportingstructure comprising three panels 500, EM and 502, and a camming plate503 which are mounted in spaced-apart relationship by means of thespacing columns 504, 505 and 506 and the assembly screws 509 and 5I0.The three panels are constructed of insulating material such as fiber orthe like and carry the electrical fixtures of the device. Morespecifically, the panel 50I carries a number of spacedapart contactpieces I3I which are concentrically mounted about the center of thepanel and are provided with inwardly disposed contact points which areadapted to be engaged by the end of a wiper I29 mounted for rotationwith the operating shaft 520 of the device. The panel 5t2 similarlysupports a number of contact pieces I32 having contact points arrangedto be engaged by the end of a wiper I 30 which is mounted for rotationwith the operating shaft 520 of the device. As schematically indicatedin Fig. l of the drawings, the contact pieces I3I and I32 are radiallystaggered about the axis of the shaft 520 while the contact making endsof the wipers I29 and I30 are in axial alignment. With this arrangement,and during rotation of the shaft 520, the contact pieces I3I and I32 arealternately engaged by their respective associated wipers I29 and I30.The two center panels 50f and 502 also carry terminal pieces 5I3 and 5M,respectively, which are provided with inwardly extending contact makingends that are biased to engage collector rings 5; and 5I8 mounted forrotation with the shaft 520. In the illustrated wiring arrangement thesetwo terminal pieces are connected together and to the control grid ofthe control tube.

The resistor elements I03 to I26, inclusive, as shown in Fig. 1 of thedrawings, are connected in series-circuit relationship and the alternatejunction points therebetween are connected to the contact pieces I3I andI32 in the order of the disposal of these contact pieces about the axisof the shaft 520. As thus arranged two resistor elements are connectedin series between each adjacent pair of contact pieces. The purpose ofusaces; 1.97

ing two series-connected resistor elementsinstead of a single element ofhigher resistance is to permit resistance matching such that theresistance connected between each adjacent pair; of contact" pieces isexactly that required to produce ade-' sired change in the pulsingrateof the relay I50. In this regard it may be noted that; due tomanufacturing variations, the individual resistors may. have resistancevalues which vary as much as 10% plusand minus from a desired standard.Thus, if it is desired, for example, to provide a resistance between twoof the contact pieces having a value of 1000"ohms, two resistor elementsof 450 and 550 ohms, respectively, may be used. In short, the elementsmaybe selected in matched pairs such that the exact desired values ofresistance between the different pairs of contact pieces may beobtained.

The resistor elements I03; I04, I05, etc., are

supported between thepanel 500 and the solder-- ing tails of the contactpieces I3I and I32. Thus the end of one lead-in wire to the resistor lowis soldered to the soldering tail of the contact piece I3Ia and theother lead-in wire to this resistor is passed through an opening inthe'panel 500. Similarly, the end of one lead-in wire to the matchingresistor element I05b is soldered to LOT the soldering tail of thecontact piece I32!) and the other lead-in wire to this element ispassedthrough an opening in the panel 500. The ends ofthe wires which extendfrom the two elements I'5a and W519 through the adjacent openings inthepanel 500- are twisted and soldered. Thus a rugged supportingstructure for the elements is provided.

For the purpose of accurately controlling the movement of the shaft 520so that, regardless of the setting thereof, the wiper I29 is accuratelypositioned to engage one of the contact pieces I3I or the wiper I30ispositioned accurately to engage one-of the contactpieces I32, 9, cammingarrangement comprising the panel or plate 503 and a cooperating cammingelement 5 I9 rigidly secured to the shaft 520, is provided. Morespecifically,

the plate 503 is provided with a number of open? ings 503a therethroughwhich are concentrically disposed about the axis of the shaft 520 andare radially aligned with the contact pieces vI3I and- I3'2- carried bythe panels L and 502. The sec tions of this plate separating theopenings 503w are filled out or raised to provide camming surfaces o'verwhich the cam finger 519a of the camming element 5I9' is adapted to rideas the'shaft 520 is rotated from one position to a succeeding 1position. More specifically, the" element 5I0 is in the. form of a steelplate constructed from flat spring steel stock, and the cam-finger 5I9acom-- prises a bent-out portion ofthe plate having a rounded edge whichis adapted. to ride over the raised camming surfaces betweenthe openings503a, and bridges one of these openings eachtime the shaft 5201sadjusted to a desired setting.

With this cammingiarra'ngement the shaft 520-- canv only be operated in"a step by-step manner since the tension of the element 5l-9 issufficient to rotate the shaft 520 until the" camming finger 5I9abridges the nearest opening 5032; in the event the shaft is operated toaposition lying between two of these settings From the above explanationit will be'under stood that the operating shaft 520 is journaled forrotation in the two panels 501 and 502 and also in the plate 503. Thisshaft is alsojournaled in: a sleeve member 52'3which is fixedlysecuredto the plate 503 and is threaded to receive an assembly nut 52?. Thearrangement for mounting' the devicev upon the sub-panel 30I comprisesau-shaped mounting bracket 52I having its legs secured to the panel 30Lby means of assembly screwsfandri-tscentral web drilled to receive thesleeve 523.

collar 522'which abuts the surface of the panel 503'and a lock washer528 as the assembly nut 52'! is screwed on the-threaded sleeve 523. Inorder to maintain exact alignment between the radial positions of thetwopanels SM and 502 which carry the contact pieces I3I and I32 and thefront panel 300 upon which a portion of the indicating arrangementreferred to above is inits outer end with a knob I33. To indicate therelationship that exists between the ground speed of the craft fromwhich the bombs are to be dropped and the spacing intervals betweenhits. onthe objective for any particular setting. f the rheostat, theindicating arrangement illustrated.

in Figs. 4 and 6 of the drawings is provided. This arrangement includesan index or indexing. plate arranged on the outer surface of the panel300-.- This-index comprises logarithmically scaled indicia designatingthe intervals between bomb hits in feet and is arranged to cooperatewith an indexing element 405 scaled at its outer pe riphera-l edge withnumerically defined indicia of the ground speed of the craft in knotsper hour. The element 405 is arranged to be driven from the shaft 520through a gear train which comprises a driving gear 530 and a drivengear 53! having a'pred'etermined ratio therebetween. More specifically,the gear 530 is mounted for rota.- tion with the shaft 520 and ispositioned to ro-' tate between the two panels 300 and SM; the gear 53Iis provided with a hub 53Ib journaled. in an openin provided in theouter panel 300 and with a rearwardly disposed hub 53Iajournaled in analigned opening provided in the sub-- panel MN; and the-indexing plate405 is mount- 7 trated apparatus is utilized to control the bomb releasemechanism I85, it may first be assumed that this mechanism is tobeselectively controlled by the bombardier of an aircraft in which theequipment is installed to release bombs from this craft selectively oneat a time. In suchcase, the master switch I58a is operated to itsclosed-circuit position; the switch I50 is operated to its selectposition wherein the contact springs I63 thereof are closed; and thecounting; device H0 is preset tothe predetermined olfnormal positionwhich correspondsto the number'of bombs that are to be dropped. Inorderto preset this device, the knob IBI is actuated to rotate the wheels Illand I I4 so thatthe pin I12 is moved to the ofi-normal positioncorresponding to the number of bombs to be released, this number beingindicated by the coincidence" its normal position, the contact springsI13 are The central web portion of the bracket piece 52I isclampedbetween a spacing windings of the vibrator I65 and the winding ofthe locking relay I40 from the current source I68. In operating, therelay I40 prepares a looking circuit for itself at its contacts I43. andcloses an obvious circuit for energizing the signal lamp I31. Whenvoltage is applied to the input side of the vibrator I65 the normalrated output voltage appears across the output terminals I651) thereofto energize the pulsing relay I50 in a circuit which includes thecontacts I63 and the resistor I64. In omrating, the relay I50 closes itscontacts I I to complete a circuit including the source I68 fortransmitting a current pulse to the bomb release mechanism I85, wherebythis mechanism is actuated to release a bomb. At its contacts I54, therelay I50 completes an obvious circuit for energizing the steppingmagnet I15. Incident to the operation of this ma net, the associatedpawl mechanism is operated to rotate the wheels HI and I-14 in adirection such that the pin I12 is moved one step nea'rer its normalposition. When the contacts of the switch I61 are opened, the relay I40,the signal lamp I31, the vibrator I65 and the pulsing relay I50. are alldeenergized in an obvious manner. The relay I50. in releasing, opens itscontacts I5I to terminate the current pulse transmitted to the bombrelease mechanism I85. At its contacts I54, the relay I50 deenergizesthe stepping magnet I15 of the counting device I10, whereby the pawlmechanism controlled by this magnet is re-- leased under the control ofthe leaf spring I80. In this regard it is noted that the suppressorcircuit comprisingthe res stor I82 and the condenser I83 connected inshunt with the contacts I54, serves to protect these contacts againstarcing and pitting during the opening and closing of the same. Thecondenser I84 is s milarly connected in shunt with the contacts I5I toprotect these contacts against arcing and pitting during the make andbreak periods thereof. The abovedescribed operations are repeated eachtime the contacts of the switch I61 are closed and then opened. Fromthis explanation it will be understood that a current pulse'istransmitted to the mechanism I85 to effect the release of a bomb eachtime the relay I50 operates, and that the pin I12 of the counting deviceI10 is moved one step nearer its normal position each time the contactsof the switch I61 are closed. After a predetermined number of operationsof this switch, the pin I12 of the counting device I 10 is rotated backto its normal position wherein the contact springs I13 are moved out ofengagement. Following the disengagement of these contact springs furtheroperation of the switch I61 is without effect to cause the operation ofthe two relays I40 and I50.

In utilizing the apparatus to control the bomb release mechanism so thata train of bombs is automatically released thereby, the counting deviceI10 is operated to the setting corresponding to the desired number ofbombs in the train; the rheostat I02 is adjusted to the positioncorresponding to the desired spacing interval between hits for theexpected ground speed of the craft during the bombing operation; thepower switch IBM is operated to its closed-circuit position; and theswitch I60 is operated to its train position wherein the contacts I6Iand I62 are closed. With the switch I68a closed and the switch I60operated to its train position, an obvious circuit including the currentsource I68 is completed for energizing the cathode heater I 00h of thecontrol tube I00 in parallel with the signal lamp I31. It is noted inthis regard that the heater I00h should be energized at least a fullminute before the bombing operation is started.

After the above-described operations are performed, the switch I61 maybe operated to initiate the release of the train of bombs. When thecontacts of this switch are closed, a circuit is completed through thecontact springs I13 for energizing the locking relay I and the primarywindings of the vibrator I65 in parallel. In operating, the relay I40closes its contacts I43 to complete a locking circuit for itself, thiscircuit extending from the positive terminal of the source I68 by way ofthe switch I68a, the contacts I62 and I43, the contact springs I13, andthe winding of the relay I40 to the negative terminal of the currentsource. After this circuit is completed, the primary windings of thevibrator I65 are also energized in a circuit which includes the contactsI13, I43 and I62. Accordingly, the switch I61 may be released withoutinterrupting or terminating the bomb release operation in progress. Atthe time the switch I61 is operated, the condenser I 34 isshort-circuited over a path which includes the contacts I53 and theencircuited resistance of the rheostat I 02. The cathode I000 and thecontrol grid I 00g are therefore at substantially the same potential.

When the primary windings of the vibrator I65 are energized and therated output voltage appears across the output terminals I65b of thevibrator, this voltage is positively applied to the screen electrodeI00s of the tube I00 over a path including the resistor I39, and thewinding of the relay I is energized by the space current flow throughthe tube I00. More specifically, the circuit for energizing this relaynow extends from the positive output terminal Ib of the vibrator I65 byway of the winding of the relay I50, the contacts I6! the space currentpath between the anode I00a and the cathode I000 of the tube I00, andthe 'encircuitecl section I Ola of the biasing resistor IN to thenegative output terminal of the vibrator I65. When thus energized therelay I50 closes its contacts I5I to transmit 3. current pulse to thebomb release mechanism I85. At its contacts I54, the relay I 50 closesthe operating circuit for the stepping magnet I15, whereby the countingdevice I10 is operated to count the current pulse transmitted to thebomb release mechanism. At its contacts I53, the relay I50 opens thepath short-circuiting the condenser I34. At its contacts I52, the relayI50 bridges the condenser I34 across the encircuited portion Iilla ofthe biasing element I 0| in series with the resistor I02 and the encircute resistance of the rheostat I02.

After the condenser I34 is thus bridged across the resistor I02 and theresistor section mm, the voltage drop appearing across these twoelements as the result of the space current flow through the tube I00causes a charging current to be delivered to the condenser through theencircuited resistance ofthe rheostat I02. As this condenser is charged,the voltage thereacross appreaches a value equaling that of the voltagedrop across the two resistor elements. In this regard it will beunderstood that the rate of the voltage build-up across the condenserI34 is determined by the amount of resistance included in the chargingcircuit, which resistance serially includes the encircuited section IOIaof the resistor IOI, the resistor I02 and the encircuited resistance ofthe rheostat I02. Thus if the series resistance of this circuit is low,the voltage across the condenser I34 will rapidly be increased to avalue approaching that of the volta e drop across the resistor sectionIOIa and the resistor I02. On the other hand, if the series resistanceof this circuit is high, a relatively much longer time interval will berequired ior the voltage across the condenser I34 to approach thevoltage drop across the resistor section IOIa and the resistor I02. Itwill be noted that the charging currentt'ra'verses-the condenser I34 ina direction such that'the' resulting voltage thereacross biasesthe-control grid I009 negatively with respect to the cathode I 000. Asthis bias voltage is increased, the space current flow 'through the tubeI is decreased to decrease the voltage drop across the resistor sectionI0la and the resistor I02, whereby the charging rate of the condenserI34 is lowered. After a predetermined time interval, required for thecondenser I34 to be charged to a voltage somewhat less than the voltagedrop across the resistor section IOIa and the resistor I02, the spacecurrent flow through the tube I00 is lowered to a value such that therelay I50 is insufiiciently energized to remain operated. The relayyl5l0accordingly restores. V

In releasing, this relay opens its contacts I M to terminate the currentpulse transmitted to the bomb release mechanism I85. -At its contactsI54, the relay I 50 deenergizes the stepping magnet I of the countingdevice I10. At its contacts I52, the relay I50 opens the above-describedcharging circuit for the condenser I34. At its contacts I53, the relayI50 completes the previously described circuit for discharging thecondenser I34 through the encircuited resistance of the rheostat I02.After this discharge path is completed the condenser I34 starts todischarge through .that portion of the rheostat resistance connected inshunt therewith, and asthe condenser discharges the voltage thereacrossdecreases. Incident to the decrease of this bias voltage between thecontrol grid I009 and cathode I000 of the tube I00, the space currentflow through the tube is increased to increase the energization of thepulsing relay I 50. Here again the rate of decay of the voltage acrossthe condenser I34 is determined by the amount of rheostat resistanceconnected in shunt therewith. If the value of this resistance is low,the condenser I34 is rapidly discharged. On the other hand, if the valueof this resistance is high the condenser I34 is only slowly discharged.Itwill be understood in thisregard that therrate of discharge of thecondenser I34 .de-'

termines the time interval'required for the space current flowingthroughthe tubeto rise toa value sufiiclent to cause the reoperation ofthe pulsing relay I50. When this value of vspace current is reached, therelay I50 reoperates toperform the functions described above. From thispoint on the above-described circuit control operations reoccur untilsuch time as the pin I12 of the counting device I10 is driven back toits normal position under the control of the stepping magnet I15. Inthis regard it will be understood that the mb release mechanism Ioperates to release a bomb are disengaged to cause the deenergization ofthe vi brator lfi5 and the relay I 40 in an obviousmanner. The relayI40, in restoring, opens its contacts I43 further to interrupt itslocking circuit and the parallel circuit for energizing the primarywindings of the vibrator I65. When this vibrator is deenergized theoutput voltage thereof is reduced to zero to cause a cessationin thespace current flow through the tube I00 and thus efiect the release ofthe pulsing relay I50. It .will be understood, therefore, thattheoperation of the illustrated apparatus to transmit current impulsesto the bomb-release mechanism I85 is terminated whenv the control pinI12 of the counting device I10 is returned to its normal positionInol'dfll to deenergizethe signal lamp I31 it is .necessaryto restorethekey I50 to its normal position wherein the contacts I6] and I62thereof arerespegtively disengaged. .From the above explanation it will.be .understood that theperiodicity of operation of the pulsing relayI50 is determined by the time constants of the circuits .for chargingand discharging the condenser I34. It will also be understood that bysuitable operation of the knob I33 to adjustthe wipers I29 and I30 alongthe contact pieces I 3| and I32, any desired portion of the rheostatresistance may be included in these circuits to change the timeconstants of these circuits accordingly. More specifically, astheencircuitecl operated and released. Converselyfas the encircuitedrheostat esi tance islowered t v d e s t time constan s o e char ing andd schar in ci its, t e at of char e. and dis har efof the con enser 4 israised-to increase thereuod ity at which thep ls ne relay I50 is ope a ae ea ed.- It ha en found from t l tests t t a substa t al y lnsarrelationshi e s betw en g ven inc ements of n e he epcircuitedrheostat resistance and the resulting inem ts of han e i t per di t oioper tion of the pulsing relay I50. In other words, changes in thepulsing rate o f this relay are directly proportional to changes in theencircuited rheostat resistance. In the illustrated arrangement. theincrements of resistance inserted in the condenser charging anddischarging circuits as the rheostat is operated step-by-step from itslow resistance setting to its high resistance settingaieprogressivelydecreased at eachstep, which means that the bomb intervalspacing for .a given ground speed of the craft is non-linearly relatedto the different positions of the rheostat control knob I 33 a t e d fer nt osit on oi he indexin Pl t 05- In th i d c t sa ra eemsnt omp s hescal 4 nd he sc e i d b th de el ment 4 the .d fiershse in th a es ofeostat r is anc td fierent eps thereof are accounted for byutilizingzlogarithmireally spaced s a e ndic awh c n th spaci stherebetween, are so related to. the pulsingrate r each s tt n o th rhost t ast provide. a

"I'heinitial calibration of the scale 404may beaccurately d t rmined byealcii atine. or a sire ground speed of the craft, the pulsing rates ofthe relay I50 which are required for the different bomb hit spacings,and then calculating or experimentally determining the increments ofrheostat resistance that are required between the different contactpieces of the rheostat to provide the desired pulsing rate at eachSetting of the rheostat. From the measured pulsing rate for each settingof the rheostat, the bomb hit spacing may then easily be ascertained andsuitably identified in the scale 404 opposite the mark of the scale 405which designates the ground speed at which the scale 004 is beingcalibrated. After the markings of the scale 404 are thus determined forone ground speed, the markings of the scale 405 may readily bedetermined, because of the direct ratio which exists between bomb hitspacing and ground speed of the craft.

As indicated by the above explanation, the resistance value of theresistor section I Ia partially determines the magnitude of the averagecurrent flow through the winding of the relay I50 during the pulsingcontact make periods thereof and hence the extent of each contact makeperiod. This arrangement forms a convenient vehicle whereby the ratio ofthe make and break periods of the pulsing contacts II, controlled by therelay I50, may be varied. Thus by decreasing the resistance value of theresistor section I Ola, the make periods of the contacts I-5I areincreased to increase the ratio of the make to break periods.Conversely, b increasing the resistance of the resistor section I 0Iaeach make period of the contacts I5I may be decreased to lower the ratioof the make to break periods.

As previously indicated, so long as the potential positively applied tothe screen e ectrode I00s of the tube is maintained substantiallyconstant, full control of the magnitude of space current flow throughthe tube I00 is obtained by varying the bias on the control grid I 00gthereof, regardless of wide variations in the voltage appearing acrossthe output electrodes I051) of the vibrator I 65. On this point it haspreviously been indicated that the voltage of the source I58 ma varyfrom its rated value by as much as plus or minus. Such variaticns in thevoltage applied to the input terminals of the vibrator I 65 will, in theusual commercial type of vibrator, result in substantial changes in thevoltage across the output terminals thereof. In the illustratedarrangement, however, such variations in the voltage of the source fromwhich the screen potential is derived do not materially change theapplied potential of the screen electrode I 00s. mediately the outputvoltage ap ears across the terminals I651) of the vibrator I65, thedischarge tube I38 is ionized. As this voltage tends to increase, due toan increase in the voltage across the terminals I65b, the currenttraversing the space current path of the tube I38 increases to increasethe voltage drop across the resistor I39. Conversely. as the voltageacross the output terminals I652) of the vibrator I85 decreases, thecurrent drawn by the tube Ithrough the resistor I39 is decreased. Due tothis action the voltage across the electrodes of the tube E38. 1. e.,that positively applied to the screen electrode 100s, is stabilized at apredetermined value which may be equal to the rated screen voltage ofthe Thus imiii) the periodicity of operation of the pulsing relay I isrendered substantiall independent of vari ations in the voltageappearing across the output terminals of the vibrator I65.

From the above explanation it will also be understood that wide changesin the temperature of the apparatus tend to vary the rate at whichimpulses are produced thereby. Thus, the measured resistance of theresistor elements I03, I 04, I05, etc., included in the timing circuit,may vary as much as twenty-two percent over the operating temperaturerange. These elements all have a positive temperature coefiicient ofresistance. Other factors tending to contribute to a change in thepulsing rate with ambient temperature variations are changes in theresistance of the resistor ml and the winding of the relay I50, andrelative displacement of the elements of the tube I00. Th net efiect ofthe various factors is the same as that obtained by using a rheostatI02, the elements of which have a substantial positive coefiicient ofresistance, i. e., the pulsing rate increases with a decrease in theambient temperature and vice versa. This efi'ect is offset by the actionof the resistor I02 included in the cathode circuit of the tube, whichhas a negative temperature coefficient of resistanceand hence the efiectof decreasing the pulsing rate of the apparatus as the ambienttemperature decreases. It has been found that by using a resistor I02 ofthe character indicated and having the proper resistance value, thepulsing rate of the apparatus is substantially unafiected b widevariations in the temperature of the apparatus.

Referring now more particularly to Fig. 2 of the drawings, the apparatusthere illustrated is substantially similar in construction andarrangement to that shown in Fig. 1 and described above. In fact, theapparatus as mechanically shown in Figs. 3 to 6, inclusive, of thedrawings may be wired either in accordance with the circuit of Fig. 1 orthat of Fig. 2, corresponding reference characters differing only in thehundreds digit being used to identify corresponding parts of the twocircuits. It will be noted that in the Fig. 2 arrangement the voltageregulating gaseous discharge tube 238, which is rovided for maintainingthe screen potential 200s of the control tube 200 constant, is connecteddirectly between this electrode and the associated cathode 2000. Thisarrangement has the advantage that the constancy of the potentialapplied to the screen electrode is measured as between this electrodeand the cathode rather than between the screen electrode and ground.Thus variations in the space current flow through the cathode resistor20I occasioned b variations in the bias applied to the control grid 200gdo not alter the potential diifen ence between the screen electrode 200sand the cathode 2000. Accordingly, the magnitude of space current flowthrough the tube 200 is determined substantially entirel by the biasapplied to the control grid 200g.

It also will be noted that in the Fig. 2 arrangement a voltage divider235 is provided which is connected between the cathode 200c and thegrounded negative output terminal 2651) of the vibrator 265. Theadjustable tap or wiper of this voltage divider is connected to thewipers of the rheostat 202 so that a variable portion of the voltagedrop across the resistor 235 is normally impressed across the electrodesof the bias determining condenser 234.

In considering the manner in which the circuit arrangement illustratedin Fig. 2 functions, it may first be assumed that the bomb releasemechanism is tobe controlled to release bombs selectively one ata time.In such lease, the power switch 268a is operated to its closed-circuitposition and the switch 250 is operated from its illustrated normalposition to its select position wherein the contacts 252a, 262D and 2620are respectively engaged. After the power switch 268a is closed, andwhen the switch 260 is operated to its select position, a circuitincluding-the contacts 262a is completed for energizing the. primarywindings of the vibrator 255 in parallel with the filament of the signallamp 231. The energization of this lamp provides a signal that theswitch 260 occupies one of its two off-normal positions. When energizingcurrent is delivered to the primary windings of the vibrator 265, anoutput voltage appears across the output terminals 26% which serves toenergize the relay 250 in a circuit which includes the resistor 239 andthe engaged key contacts 2620. In operating, the relay 250 closes itscontacts to prepare the available circuit for transmitting currentimpulses to the bomb release mechanism 285. At its contacts 254 and 255,the relay 250 prepares the operating circuit '25! to the bornb releasemechanism 285, whereby this mechanism is actuated to release a bomb. Theremaining circuit switching operations performed by the relay 240 are ofno effect in the case under consideration wherein the switch 250occupies its select position. When the contacts of the switc'h261 areopened, the relay 240 is deenergized in an obvious manner. In releasing,

this relay opens its contacts 24I to interrupt the current pulsetransmitted to the bomb release mechanism 285. In this regard it isnoted that the condenser 284 shunting the series-connected contacts 24!and 25! serves to protect the contacts 24! against arcing and pitting asthese contacts are opened and closed to transmit current impulses to thebomb release mechanism. The above-described operations are repeated eachtime the contacts of the switch 261 are closed and then opened. Fromthis description, it will be understood that a current impulse istransmitted to the release mechanism 285 each time the switch 261 isoperated and then released to cause the operation and release of therelay 240. This mechanism responds to each received impulse by releasinga single bomb. After the desired number of bombs have been dropped, theswitch 260 may be restored'to its normal position to cause thedeenergization of the vibrator 265, the relay 250 and the signal lamp231.

In utilizing the apparatus illustrated in Fig.2 of the drawings tocontrol the bomb release mechanism 285 so that a train of bombs isautomatically released thereby, the power switch 258a is operated to itsclosed circuit position; the counting device 210 is operated to thesetting corresponding to the desired number of bombs in the train; therheostat 202 is adjusted tothe posirtion'correspondin-g to the desiredspacing interval-between bomb hits for theexpected ground speed. of. thecraft during the bombing operation; andthe switch v260 is operatedto'its train position wherein thecontacts 261a, 26H) and 261a arerespectively engaged. With the power switch 268a closed and the countingdevice 210 preset so that the control pin 212 thereof occupies anoff-normal position, a circuit including the contacts 213a is completedfor energizin the oathode heater 201371 the signal lamp 231, and theprimary windings of the vibrator 265 in parallel. It is noted in thisregard that the cathode heater 2007]. should be energized at least afull minute before the bombing operation is started.

Following the operations just described, and when the rated outputvoltage of the vibrator 265 appears across the output terminals 255!)thereof, this voltage is positively applied to the screen electrode 200sof the tube 200 over a path including the resistor 239, and the relay250 is energized in a circuit which includes the space current path ofthe tube 200 and the voltage dividing resistors 235 and 20l in parallel.When thus energized the relay 250 closes its contacts 25l to prepare thecircuit for'transmitting current impulses to the bomb release mechanism285 and, at its contacts 254 and 255, prepares the operating circuit forthe stepping magnet 215 of the counting device 210 and a circuit forenergizing the relay240. At its contacts 253, the relay 250 opens apoint in the circuit over which the condenser 234 may be discharged. Atits contacts 252, the relay 250 prepares a circuit for charging thiscondenser to a value approaching that appearing across the resistorsection 20m and the resistor 202, which results fro-m space current flowthrough the tube 200.

After space current flow through the tube has been initiated in themanner explained above, the space current traversing the resistor 202'and the resistor section 20hr of the biasing element 20! produces avoltage drop across these series connected elements which is impressedacross the voltage dividing resistor 235. A portion of this voltage, i.e., that appearing across the resistor section 235a, is impressed acrossthe electrodes of the condenser 234 through the encircuited resistanceof therheostat 202. After a short time interval, and before the bombrelease switch 261 is operated, the condenser 234 is charged to the fullvalue of the voltage across the resistor section 235a. This voltage, itwill be noted, is negatively appliedto the control grid'ZOBg of the tube205 to reduce the space current flow through the tube. .By adjusting thewiper along the voltage dividing resistor 235, the extent of this biasvoltage may .be varied at will. Preferably this adjustment is so carriedout that the magnitude of the space current flowing through the tube 203only slightly exceeds "that required to operate the re1ay250 after thisrelay has been released. The purpose of thus preliminarily biasing thecontrolv grid 203g by charging the condenser 234 to a predeterminedvalueis that of preventing the first release period of the relay 25!],following the operation of the bomb release switch 261, from beingunduly long.

After the'above-described operations are completed, the bombreleaseswitch 261 may be operated to initiate the release of the trainof bombs. When the contact of this switch are closed a circuit iscompleted through'the contacts 26) and 21311 for energizing the lockingrelay 240 from the current source 268. In operating, the reassent?ia-y5240 closes its contacts to complete a locking circuitiforitselfwhich extends fromthe positive'terminal of the source 268by'way of thepower switch 258a, the contacts 2610, 243 and 213b,.and-the winding ofthe relay .240't0 the negative terminal of the SOUICeI'ZfiB. Aparallelbranchof this circuitextends through the contacts"2.55.and 24.5. .Afterthis locking circuit is established, the switch 26'! may bereleasedWithout interrupting or terminating the bomb. release operationzinprogress. '-At its contacts 241, the relay .240 rClOSBS the-above-described circuit for transmitting ascurrent pulse to the bombrelease mechanism 1285. At its contacts 246, the relay shuntsthe'contact springs2T-3a of the counting device to complete obviousmultiple circuits for fin 'gizing the cathode heater 20th, the signal'1amp,,237 and thaprimary windings'of the vibrator 26,5. At ,-itscontacts-244, the relay 240 completes theprepared operatingcircuit forthe stepping magnet .215, this circuit extending from the .Dosiiveterminal of the current source .268 by .thus energized, the countingdevice 210 is operated to count the current impulse transmitted'to thebombrelease mechanism 285.

At its contacts .242, the relay-240, in operating, completes thepreviously mentioned circuit for charging the condenser 234 to a voltagesufi'icient to cause .the release of the pulsing relay 2 50. Thus whenthese contacts are closed, the condenser 234 is bridged across theresistor 202 and the resistor section 201a of the biasing element 2!over a path. which includes the encircuited resistance of.,the rheostat232 and the contacts 252 242 and 2am. It will be noted that incident tothis switching operation, the lower portion 2351i .Q the resistor 2 3.5is short-circuited and the series resistor elements 202' and 2am areconnected directly in parallel with the resistor 235a. The resistancevalue of the resistor section 235a is, however, several times that ofthe series resistance of the two resistor elements 202' and 20m, andhence the time constant of the condenser chargins circuit is notmaterially influenced by the resistor section 235a. When theabove-described charging circuit is completed, the voltage across thecondenser 234, i. e., the bias voltage negativelyapplied to the controlgrid 200g, starts to rise at a rate determined by the setting of therheostat 202. Here again if the encircuited resistance of he rheostat202 is low, such that the series resistance of the charging circuit issmall, the voltageacross the condenser 234 will rapidly rise to a. valueapproaching that of the voltage drop across the resistor elements .202and 2am. On the other hand, if the encircuited resistance of therheostat 202 is high, a relatively much longer time interval will berequired for the voltage 'across'the condenser 234300 rise to a valueapproachingthe voltage drop across the resistor elements 2112f and20|a..After a predetermined time interval, determined by the time constant ofthe charging circuit and henceby the setting of the rheostat 202, thebiasvoltage across the condenser -2 34 15 increased to a point such thatthe space current flow through the tube .202 is insufiicient to retainthe pulsing relay 253 in its operated po- -srtron. This relayaccordingly restores.

In releasing,.the relay 250 opens it contacts 251 to terminate thecurrent pulse transmitted to thebembrelease mechanism 285. At itscontacts255, the relay 250 opens one of the locking circuits for therelay "240. Atits contacts 254, the relay 250 deenergizes the steppingmagnet215 of the counting device210. At its contacts 252, the rela-y25llopens the above-described charging circuit for the condenser 234. At itscontact 253, the relay 250 completesan obvious circuit for dischargingthe condenser234 through the encircuited resistance of the rheostat 202.After this condenser discharge circuit is established, the condenser 23i-starts to discharge through that portion of the rheostat resistanceconnected in shunt therewith, and as it discharges the Voltagethereacross decreases. Incident to the decrease of this bias voltagebetween the control grid 200g and .the-cathode-Zliilc of the tube 20!],the space current flow through the tube rises to increase theenergization of the pulsing relay 25ll. Here again, the rate of decay ofthe voltage across the condenser 234 is determined by the amount ofrheostat resistance connected in shunt therewith. Thus if the valueofthis resistance is low the condenser 234 isra-pidly. discharged. Onthe other hand, if the value of thisresistance is high the condenser 234is only slowly discharged. It will be understood in this regard that therate of discharge of the condenser 234 determines the time intervalrequired for the space current flowing through the tube 200 to rise to avalue sufficient to cause the reo-perationof the pulsing relay 250. Whenthis value of space current is reached, the relay 25E] reoperates toperform the functions de scribed above. From this point on theabovedescribed circuit control operations reoccur until such time as thepin 272 of the counting device 210 is driven back to its normal positionunder tacts 255 to shunt the contact springs 21% of the counting device219 and thus establish the above-described multiple locking circuit forthe relay 240. Thus the relay 240 is prevented from releasing toprematurely terminate the current pulse being transmitted to the bombrelease mechanism 285, in'response to the separation of the contactsprings 21312 which occurs shortly after the last operation of the relay250. In this regard it will be noted that when the counting device 210is operated to count the last current pulse transmitted to the bombrelease mechanism 285, the pin 212 is returned to its normal position toeifect the disengagement of the contact springs 21312 and 213a,respectively. At the contact springs 2130:, the initially completedcircuit for energizing the primary windings of the vibrator 265 inparallel with the filament of the lamp 231 and the cathode heater 20072,is opened. This circuit is, however, held closed at the'contacts 246 ofthe locking relay. When the relay 25B thereafter releases to terminatethe last current pulse transmitted to the bomb release mechanism 285, itopens its contacts 255 to interrupt the only remaining locking circuitfor the locking relay The relay 240 now restores and impulsetransmission to the release mechanism 285 is terminated. In releasing,this relay opens its contacts 246 to deenergize the cathode heater29671, the lamp 23'! and the primary windings of the vibrator 265.Following the release of the relay 240, the key 260 may be returned toits normal position completely to restore the apparatus to normal, orthe counting device 210 may be reoperated to a desired setting and thebomb release key 261 operated to initiate the release of another trainof bombs. The manner in which these operations may be performed, and theoperations resulting therefrom, will be clearly apparent from thepreceding explanation.

From the above description it will be understood that the effect ofvarying the encircuited resistance of the rheostat 202 is exactly thesame as that obtained by varying the encircuited resistance of therheostat I02 in the Fig. 1 circuit arrangement. This efiect, it will berecalled, is that of changing the periodicity at which the currentpulses are transmitted to the bomb release mechanism 285. It is alsopointed out that the resistor 202, having a negative temperaturecoefficient of resistance, functions in the same manner as thecorresponding resistor I02 of the Fig. 1 arrangement, in that itprevents the pulsing rate of the apparatus from being substantially.altered as a result of wide variations in the temperature of theapparatus. It will be noted further that the efiect of varying theresistance of the encircuited portion mm of the biasing resistor 2D! isalso the same as that. realized by changing the setting of theadjustable resistor I OI provided in the Fig. 1 circuit arrangement.Thus it will be apparent that by changing the setting of the adjustableresistor the ratio between the make and break periods of the pulsingcontacts f may be varied as desired.

While two embodiments of the invention have been disclosed, it will beunderstood that various modifications may be made therein which arewithin the true spirit and scope of the invention.

What is claimed is:

1. In a circuit for automatically controlling the bomb release mechanismof an aircraft to release at timed intervals a train of bombs that areto hit an objective with a predetermined but variable spacingtherebetween for different ground speeds of the aircraft, a networkcomprising an electronic interrupter having a time constant whichdetermines the time interval separating the release of successive bombsof the train, a stationary indexing element, a movable indexing element,one of said indexing elements having indicia thereon which indicatesdifierent ground speeds of the aircraft and the other of said elementshaving indicia thereon which indicates different spacing intervalsbetween bomb hits on the objective, and means controlled in accordancewith the movement of said movable indexing element for adjusting thetime constant of said circuit so that the spacing interval between hitson the objective is that indicated by said other indexing element forthe ground speed at which the aircraft is traveling.

2. In apparatus for automatically controlling the'bomb release mechanismof an aircraft to released at timed intervals a train of bombs that areto hit an objective with a predetermined but variable spacingtherebetween for each of a plurality of different ground speeds of theaircraft, a vacuum tube interrupter for determining said timedintervals, a circuit network for said interrupter including anadjustable circuit element for varying the interval separating therelease of successive bombs of the train, a plurality of indi-- catingelements each designating a different ground speed, a scale graduated interms of bomb;

hit spacing, and means for adjusting said adjust able circuit elementand for correspondingly changing the relative positions of said scaleand said indicating elements so that the bomb hit spacing for each ofsaid difierent ground speeds is indicated thereby.

3. In apparatus for automatically controlling the bomb release mechanismof an aircraft to release at timed intervals a train of bombs that areto hit an objective with a predetermined but variable spacingtherebetween for each of a plurality of different ground speeds of theaircraft, a vacuum tube interrupter including an adjustable circuitelement for varying the interval separating the release of successivebombs of the train, a plurality of indicating elementseach designating adifferent bomb hit spacing, a scale graduated to indicate differentground speeds of the aircraft, and means for adjusting said. adejustable circuit element and for correspondingly changing the relativepositionsof said scale and said indicating elements so that therelationship between the different bomb hit spacings and the groundspeeds of the aircraft are indicated at any setting of'said adjustablecircuit element.

4. In apparatus for automatically controlling the bomb release mechanismof an aircraft to release at timed intervals a train of bombs that areto hit an objective with a predetermined but variable spacingtherebetween for each of a plurality of different ground speeds of theaircraft, an electronic'interrupter including an adjustable circuitelement for varying the interval separating the release of successivebombs of the train, a scale graduated in terms of bomb hit spacing, acooperating scale graduated to indicate different ground speeds of theaircraft, and means for adjusting said adjustable circuit element andfor correspondingly changing the relative positions of said scales sothat the relationship between the different bomb hit spacings and thediiierent ground speeds of the aircraft are indicated at any setting ofsaid adjustable circuit element.

5. In a circuit for automatically controlling the bomb release mechanismof. an aircraft to release, at timed intervals 9. train ofbombs that areto hit an objective with a predetermined spacing therebetween, a networkhaving elements establishing a time constant whichdetermines the timeinterval separatingthe release of successive bombs of the train,adjustable indicating means adapted to be set to indicate the groundspeed of the aircraft, means controlled in accordance with the operationof said indicating means for adjusting said elements to vary the timeconstant of said network so that the time interval separating therelease of successive bombs of the train is adjusted to the ground speedof the air. craft to maintain said predetermined spacing between bombhits on the objective, and temperature compensating means forcompensating for changes in said elements resulting from temperaturevariations thereby preventing wide variations in the temperature of theelements of-the circuit from altering the rate at which bombs arereleased in trains.

6. In a circuit for automatically controlling the bomb release mechanismof an aircraft to release at timed intervals a train of bombs that areto hit an objective with a predetermined but variable spacingtherebetween for a given ground speed of the aircraft, a network havingcircuit elements establishing a time constant which determines the timeinterval separating the release of successive bombs of the train.adjustable indicating means adapted to be set to indicate difi'erentspacings between bomb hits on the objective, means controlled inaccordance with the operation of said indicating means for adjustingsaid elements to vary the time constant of said net work so that thespacing interval between hits on the objective corresponds to thesetting of said indicating means when the aircraft is traveling at saidgiven ground speed, and temperature compensating means for compensatingfor changes in said elements resulting from temperature variationsthereby preventing wide variations in the temperature of the elements ofthe circuit from altering the rate at which bombs are released intrains.

7. In a system for transmitting impulses over a control circuit, acircuit including an electronic pulser and adjustable timing means fordetermining the rate at which impulses are transmitted over said controlcircuit, adjustable indicating means adapted to be set to indicate therate of impulse transmission over said control circuit,

means controlled in accordance with the operation of said indicatingmeans for imparting a corresponding setting to said timing means, andtemperature compensating means for compensating for changes in saidcircuit resulting from temperature variations thereby preventing therate of impulse transmission over said control circuit from varying dueto changes in the temperature of the elements of said second-namedcircuit.

8. In a system for transmitting impulses over' a control circuit, anelectron discharge tube including an anode. a cathode and a controlelectrode, an output circuit including said anode and cathode and acontrol device for transmitting im pulses over said control circuit, aninput circuit including a timing network controlled by said controldevice to vary the bias voltage on said control electrode so that saidcontrol device is periodically operated and released, and meanscomprising a temperature compensating device common to said input andoutput circuits for compensating for changes in said circuits resultingfrom temperature variations thereby preventing ambient temperaturevariations from substantially altering the periodicity of operation ofsaid control device.

9. In a system for transmitting impulses over a control circuit, anelectron discharge tube including an anode, a cathod and a controlelectrode, an output circuit including said anode and cathode and acontrol device for transmitting impulses over said control circuit, aninput circuit including a timing network controlled by said controldevice to vary the bias voltage on said control electrode so that saidcontrol device is periodically operated and released, means foradjusting the ratio between the operated and nonoperated intervals ofsaid control device without substantially altering the periodicity ofoperation of said control device, and means comprising atemperaturecompensating device common to said input and output circuits forcompensating for variations in said circuits resulting from temperaturechanges thereby preventing ambient temperature variations fromsubstantially altering th periodicity of operation of said controldevice.

10. In a system for transmitting impulses over a control circuit, anelectron discharge tube including an anode, a cathode and a controlelectrode, an output circuit including said anode and cathode and acontrol device for transmitting impulses over said control circuit, aninput circuit including a timing network controlled by said controldevice to vary the bias voltage on said control electrode so that saidcontrol device is periodically operated and released, a resistor havinga negative temperature coefiicient of resistance and included in saidoutput circuit, thereby preventing changes in temperature of theelements of said circuits from altering the periodicity of operation ofsaid control device, and an adjustable resistor included in said outputcircuitin series with said firstnamed resistor, said serially relatedresistors being bridged by said timing network.

EDWARD S. PETERSON.

